In the 1930s, scientist and explorer Dr. Bruce Dickson attempts to climb Mount Kalpurthia in the Himalayas. There, he encounters the lost civilization of Kalahia, which possessed extremely advanced technology. The Kalahian people expose him to a mutagenic substance which alters his body to give him the same physical abilities as they had: eternal youth, and tremendous physical resilience and flexibility, including the ability to become "thin", or rather, flat.

Dickson learns much of their advanced technology, and falls in love with Olalla, daughter of the Kalahians' leader. He and his new love travel to the outside world and become superhero contemporaries of Captain America, the Human Torch, the Sub-Mariner, and others. The Thin Man, which Dickson has adopted as his superhero name, becomes a member of the stateside team the Liberty Legion during World War II.[1] The Liberty Legion then began battling Nazi agents in the USA.[2] With the Liberty Legion, he battled the Invaders, who were hypnotically controlled by the Red Skull.[3] In 1942, the Liberty Legion encountered the Thing who had traveled back in time, and then aided them in battling Master Man, U-Man, and Skyshark.[4] The Liberty Legion also battled Iron Cross.[5]

At some point, the Thin Man reveals to Captain America[6] that Olalla, whom he has married, had returned to Kalahia. The Thin Man remained in order to serve his country, and when he returns to Kalahia after the war he finds that the Nazis had located the valley and slaughtered all its inhabitants, including his wife. After this, he becomes an obsessed Nazi hunter for decades, eventually discovering that an old foe, the Nazi's Agent Axis, had been responsible for Kalahia's destruction. With the help of Captain America, he tracks down and confronts Agent Axis. The war criminal brags that since he had been brought to America under Operation Paperclip, he cannot be prosecuted for his wartime activities. The Thin Man becomes so outraged that he wraps his pliable body around Agent Axis and snaps his neck. Shocked, Captain America immediately brings him to the authorities for murder.[7]

He eventually is pardoned so that the U.S. government can obtain his knowledge of advanced Kalahian technology.[8] He is made a member of the New Invaders, and begins to contribute his knowledge to the group. Unfortunately, the entire operation was actually a ruse by the ex-Nazi villain the Red Skull, who had disguised himself as the Secretary of Defense. Once this deception is revealed, Dickson forges ahead with the plan to create a new Invaders unit armed with Kahalian technology, specifically to thwart the Red Skull and his organization, the Axis Mundi. Dickson designs the battleshipInfiltrator, which can travel through multi-dimensional space, effectively allowing it to teleport long distances; the Infiltrator is sacrificed when it is rammed into a doomsday weapon in order to protect the Earth from another World War II-era supervillain, U-Man.[9]

Bruce Dickson has been genetically modified through a scientific process developed by the people of Kahalia, to be able to convert the mass of his entire body into a highly malleable state at will, enabling him to stretch, deform, expand, or compress all or any part of his body into any shape. His costume is made of an unknown Kahalian fabric that stretches and contracts in size as he does. He most often uses his power to elongate portions of his body to the thinness of an average sheet of typing paper, enabling him to pass under a shut door. The limits on the Thin Man's powers are unknown. He can absorb the impact of a projectile shot at him or of any concussive force, within certain unknown limits, by deforming his body. When underwater he can resist intense water pressure to a superhuman extent for a period of minutes. He can become nearly two-dimensional, while his limbs can effectively become blades in the process.

He does not age and is seemingly immune to all known diseases. Thin Man has tremendous knowledge of the advanced sciences and technology of Kalahia, but only what he could memorize or take with him. All else is now lost.

The Thin Man is a good hand-to-hand combatant who has received coaching from the Patriot and Miss America. He is also an accomplished airplane pilot.